1. Field of the Invention
The present invention relates to a liquid droplet ejection head and an image forming apparatus, and more particularly, to a structure of a liquid droplet ejection head in which a plurality of liquid droplet ejection ports (nozzles) are arranged two-dimensionally at high density, and an image forming apparatus which forms an image on a recording medium by means of liquid droplets ejected from the liquid droplet ejection head.
2. Description of the Related Art
Japanese Patent Application Publication No. 4-329151 describes a recording apparatus having a recording head which combines a spray mechanism for white ink only, which uses a piezoelectric element, and a spray mechanism for a dye sublimation coloring material, which uses a heat generating resistance element. This recording apparatus forms colored ink by causing white ink and coloring material sprayed from the recording head to collide with each other during flight, in such a manner that recording is performed by means of the colored ink landing on a recording medium.
Although Japanese Patent Application Publication No. 4-329151 discloses a structure of a recording head comprising a spray mechanism using a piezoelectric element and a spraying mechanism using a heat generating resistance element, it does not describe a high-density arrangement of ejection ports or pressure chambers.
In general, the ejection method using piezoelectric elements (a “piezo” method) has the merit of allowing a great deal of freedom in the selection of the material of the ejection liquid; however, the piezoelectric elements and pressure chambers are large in size, and in the case of a head composition which ejects two liquids, it is difficult to achieve a high-density arrangement of the pressure chambers.
As opposed to this, a method (thermal method) which heats a liquid by means of a heat-generating element and ejects the liquid by means of the gas bubbles formed by film boiling makes it relatively easier to achieve high density, compared to the piezo method described above; however, since it is necessary to boil the ejection liquid, the amount of freedom in selecting the ejection liquid is reduced.
Japanese Patent Application Publication No. 10-24564 discloses a method and structure of an ejection head for achieving same, whereby two types of liquids, which are reactive, are combined within the head and are ejected from ejection ports, recording being performed by means of the ejected liquid landing on a recording medium.
However, since the two types of reactive liquid are combined inside a flow channel connected to an ejection port (nozzle), there is a possibility that blockages may occur due to the combined reaction of the two liquids. Hence, from the viewpoint of avoiding blockages of this kind, a method is desired in which the two liquids are combined after ejection.